Field of the Invention
The invention lies in the field of printing. The invention relates to an apparatus for printing, in particular, a franking and/or addressing machine. The printing apparatus has a printing head constructed for achieving the relative movement between the printing head and the medium to be printed to be capable, during printing, of being moved between a first longitudinal position and a second longitudinal position in a given direction with respect to a base element. The printing head is at the same time guided by a first guide device. An offsetting device allowing the printing of printing images offset to one another transverse to the given direction and overlapping one another at most in an edge region is also provided. The offsetting device is constructed for offsetting the printing head relative to the base element from a first transverse position into at least one second transverse position spaced from the first transverse position transverse to the given direction. The present invention relates, furthermore, to a method for printing.
Within the meaning of the invention, the term xe2x80x9cprinting headxe2x80x9d designates all types of printing devices that can generate a printing image on a medium. In other words, the term, on one hand, includes printing devices employing any desired printing techniques. Nor is the term restricted to the component that directly generates the printing image, but may additionally embrace further components required for generating the printing image. Such components may include, for example, ink reservoirs, etc.
A generic printing apparatus and a generic method for printing are disclose, for example, from European Patent Application EP 0 933 210 A2. In the apparatus described there, the printing head is disposed displaceably in a mounting guided by a guide rod. In order to print, the mounting, and, therefore, the printing head, is moved in a first direction, to be precise parallel to the guide rod.
When a first printing image has been generated, the printing head is offset relative to the mounting perpendicularly to the first direction in order to generate, in a further step, a second printing image with the printing head being moved in a direction opposite the first direction. The offset of the second printing image to the first printing image is of a size such that the two printing images overlap at most in an edge region in which they are contiguous to one another transverse to the first direction. It is thereby possible, by using such a printing head, to generate an entire printing image, of which the dimension transverse to the first direction, that is to say transverse to the printing direction, corresponds approximate to double the printing width of the printing head.
In the prior art apparatus, the offsetting device is disposed on the mounting and is constructed as a linear drive that acts on the printing head.
The configuration, on one hand, has a disadvantage that, during printing, a relatively high mass has to be moved using the additional linear drive on the mounting. Such movement has an adverse effect on the vibrational behavior of the drive and, therefore, on the printing image and/or on the outlay necessary for compensating the disadvantage. Additionally, limits are placed on the accelerations that can be achieved. Thus, there is a corresponding limitation on the printing speed.
Another disadvantage lies in the complicated configuration of the mounting. The mounting, while having as low a mass as possible, and, therefore, as small a construction volume as possible, must make a transverse guide available for the printing head. When exchangeable printing heads, such as, for example, ink-jet cartridges, are used, in order to avoid an excessively complicated exchange of the printing head or to make it possible to use a standard printing head, the heads must sometimes be produced in two parts with a separate receptacle, driven by the linear drive, for the printing head.
It is accordingly an object of the invention to provide a printing apparatus and a printing method with a movable printing-head guide that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that make it possible to carry out rapid and high-quality printing with a low outlay.
With the foregoing and other objects in view there is provided, in accordance with the invention, a an apparatus for printing, particularly, a franking machine, including a base element, a guide device moveably connected to the base element, a printing head, the guide device moving the printing head, during printing, between a first longitudinal position and a second longitudinal position in a given direction with respect to the base element to effect a relative movement between the printing head and a medium to be printed, and an offsetting device for printing images offset to one another transverse to the given direction and overlapping one another at most in an edge region of the images, the offsetting device connected to the printing head and offsetting the printing head relative to the base element from a first transverse position into at least one second transverse position spaced from the first transverse position in a direction transverse to the given direction, and the offsetting device connected to the guide device for offsetting the guide device.
The invention is based on the technical teaching that a high-quality print is achieved at relatively low outlay when using a generic apparatus when the offsetting device is constructed for offsetting the first guide device.
By virtue of the refinement according to the invention, during printing, only the printing head is to be moved, in particular, to be accelerated. Because the mass to be moved is, in such a case, lower than the prior art apparatus, the tendency of the system, including the printing head and its drive, to vibrate is reduced. Thus, higher accelerations can be achieved, which leads to a quicker printing operation. Additionally, the configuration reduces the outlay for any damping measures.
Moreover, only a simple standard mounting has to be provided for the printing head, insofar as it is made exchangeable, because the latter does not have to be moved relative to the mounting. Such a configuration further reduces the mass to be moved and the outlay involved in producing the apparatus.
In accordance with another feature of the invention, the offsetting device is constructed such that the offset for the first guide device takes place essentially in one plane. Such a configuration is advantageous in view of the printing operation because there is no resulting change, during the offsetting of the printing head, in spacing from the medium to be printed, which, where appropriate, would have to be compensated. Moreover, the necessary construction space for the apparatus then remains small because space does not have to be kept free for a projecting offsetting movement transverse to the actual offset direction.
The movement of the guide device during offsetting may take any desired form, and, in particular, it may follow any desired path curve. Preferably, the offsetting device is constructed for the parallel offsetting of the first guide device, in other words, in substantially mutually parallel positions. In such a case, by virtue of the simple movement sequence, it is possible for the guide device, and, therefore, the printing head, to be positioned without difficulty.
The parallel guide can be implemented in various ways. Thus, for example, one or more corresponding guide rails or the like may be provided for the guide device, which impart a straightforward translational movement to the latter during offsetting.
A particularly simple and robust refinement that is less susceptible to faults is obtained when the offsetting device includes a planar four-membered articulated mechanism that ensures guidance during the offsetting of the guide device. Such an articulated mechanism manages with simple rotary or pivot joints while ensuring a high degree of movement accuracy. As a result, in particular, incorrect angular positions of the guide device in the respective transverse positions are counteracted. Correspondingly, incorrect angular positions of the printing images in relation to one another are also counteracted. In particular, a parallel guide can be implemented in a simple way by using such an articulated mechanism.
The guide device may be connected indirectly or directly to the offsetting device in any desired way. It may, for example, be fastened directly to that member of the articulated mechanism that itself executes the desired offsetting movement. In the case of variants of the apparatus according to the invention that are advantageous because they have a simple construction, the first guide device itself forms a member of the articulated mechanism. For such a purpose, it may, for example, be directly connected at both ends to two further members belonging to the articulated mechanism.
The offsetting device can be constructed in various ways in terms of its drive for offsetting the guide device. Thus, for example, one or more separate driving devices that bring about the offsetting movement may be provided. In accordance with a further feature of the invention, the offsetting device is constructed for offsetting the first guide device by a movement of the printing head in the given direction. Thus, it is unnecessary to have a separate drive for the offsetting device. Instead, the drive for moving the printing head is also utilized for operating the offsetting device.
To achieve the offsetting movement of the guide device by movement of the printing head in the given direction, a multiplicity of refinements may be envisaged. Thus, for example, a second guide device may be provided, which is disposed on the printing head or its mounting and cooperates with a third guide device to achieve the offsetting movement. The third guide device is disposed fixedly in or on the apparatus such that, during the movement of the printing head in the given direction, a relative movement occurs between the second and the third guide device. The active surfaces of the second and third guide devices are then disposed such that, during the movement of the second and third guide devices in the given direction relative to one another, a force component occurs transverse to the given direction and is imparted by the second guide device to the printing head and through the latter to the first guide device. The force component transverse to the given direction then brings about the offsetting of the first guide device.
In the variant mentioned, a compensating device is provided that compensates the offset between the drive and the printing head during the offsetting of the first guide device. Additionally or alternatively, the entire drive may be offset correspondingly together with the guide device.
In preferred variants of the apparatus according to the invention, a driving device for moving the printing head in the given direction is provided, which is itself constructed such that it offsets the first guide device by movement of the printing head in the given direction. Offsetting of the driving device or a corresponding compensating device thereby becomes unnecessary.
Preferably, at the same time, the driving device is constructed as a traction drive with at least one traction device running through at least one first deflecting device. The printing head is then connected, in a first connection region, to the traction device such that when the first connection region runs over the first deflecting device, the first guide device is offset transverse to the given direction by being taken up through the printing head.
The connection between the traction device, for example, a toothed belt, and the printing head may be made, for example, through a connecting device, such as a connecting pin. The pin is disposed rotationally movable on the printing head or the traction device, or on both. When the first connection region runs over the first deflecting device, the connecting pin is moved transverse to the given direction in a way predetermined by the deflecting device. The connecting pin then acts as a take-up device by imparting its movement transverse to the given direction to the printing head and, therefore, also to the first guide device connected to the latter.
The first deflecting device, the further guide of the traction device and the connection between the traction device and the printing head or the printing-head mounting are preferably constructed such that the offset of the connecting device corresponds to the desired transverse offset of the printing head. As a result, the desired offset transverse to the given direction is imparted to the printing head in a simple way without further additional measures.
The deflecting device may be formed of one or more guide tracks, deflecting rollers, or the like. Preferably, the first deflecting device is constructed as a deflecting roller. The axis of rotation of the deflecting roller runs essentially perpendicular to the offset plane of the first guide device. At the same time, the offset of the guide device and, therefore, also the printing head then corresponds in a simple way to the offset that the connecting device undergoes between the printing head and traction device.
Preferably, the first deflecting device is disposed in a region of the first longitudinal position of the printing head to achieve thereby as small a construction space at the apparatus as possible in the given direction.
The driving device may be constructed as an open traction drive that is operated with an alternating driving direction, in order to return to the initial position again after one or two complete prints. In advantageous variants, the driving device is constructed as a closed traction drive because it has a simple makeup. As such, the second deflecting device for offsetting the guide device transverse to the given direction is provided, which causes the guide device to be offset back into the initial position. The traction drive can then be driven both in one direction and alternately in both directions. In accordance with an added feature of the invention, the second deflecting device is disposed in a region of the second longitudinal position of the printing head.
It goes without saying that the traction device may also be guided through further deflecting devices when, for example, the complete print is to be composed of more than two printing images disposed next to one another transverse to the given direction.
With a view to as small a construction space of the apparatus as possible in the given direction, the second deflecting device is preferably disposed in the region of the second longitudinal position of the printing head.
To ensure that the guide device and, therefore, the printing images generated using the printing head are reliably aligned with one another, in advantageous variants of the apparatus according to the invention a fixing device is provided for fixing the guide device in the respective transverse position.
In beneficial refinements, the fixing device includes in each case at least one stop for the guide device in the respective transverse position and at least one prestressing device for prestressing the guide device against the respective stop. The prestressing device may be constructed such that it is prestressed by a prestressing device, for example, a spring or the like, against the first guide device located in one of the desired transverse positions. Thereby, a change in position of the first guide device is prevented.
The prestressing device may still be constructed such that the force exerted by the offsetting device onto the first guide device during offsetting, which, between the desired transverse positions, is sufficient to remove the prestressing device from the path of movement of the first guide device counter to the prestressing force of the prestressing device. In other words, the prestressing device may be constructed such that, during the desired offsetting operations, it is forced out of the way of the first guide device by the latter.
With the objects of the invention in view, there is also provided, a method for printing, in particular, a method for making a franking impression, including the steps of guiding, with a guide device, a printing head to print a first printing image between a first longitudinal position and a second longitudinal position in a given direction and to print at least one second printing image offset to the first printing image in a direction transverse to the given direction and overlapping the first printing image at most in an edge region of the first printing image, and offsetting the printing head from a first transverse position into at least one second transverse position spaced from the first transverse position in a direction transverse to the given direction by offsetting the guide device transverse to the given direction.
The invention relates, furthermore, to a method for printing, in particular, a franking impression, in which a printing head for printing a first printing image is moved, guided by a first guide device, in a given direction between a first longitudinal position and a second longitudinal position. To print at least one second printing image offset to the first printing image transverse to the given direction and overlapping with the first printing image at most in an edge region, the printing head is offset from a first transverse position into at least one second transverse position spaced from the first transverse position transverse to the given direction. According to the invention, at the same time, the first guide device is offset transverse to the given direction for offsetting the printing head transverse to the given direction.
In accordance with an additional mode of the invention, offsetting takes place in one plane, because it results in the desired end position being reached quickly. Additionally, the movement space to be kept free for such a movement can be kept small for such a movement profile. Thus, a small construction space for an apparatus operating under the method results. Various points in time at which the offsetting of the first guide device can take place may be envisaged. Thus, the offsetting of the first guide device may take place after the movement of the printing head between the first and second longitudinal positions and the return into the first longitudinal position. A particularly simple and, therefore, rapid movement sequence or a rapid printing operation occurs preferably when the offsetting of the first guide device takes place after, preferably, immediately after, the movement of the printing head between the first and second longitudinal positions. The features are all the more so when, in further preferred variants, the offsetting-back of the first guide device takes place after, preferably, immediately after, the movement of the printing head between the second and first longitudinal positions.
Advantageously, the offsetting of the first guide device takes place as result of the movement of the printing head in the given direction. Therefore, a further drive for offsetting becomes unnecessary.
In accordance with yet another mode of the invention, the guide device is offset by a movement of the printing head in the given direction.
In accordance with a concomitant mode of the invention, at least two printing images are printed offset to one another transverse to the given direction by driving the printing head with a closed traction drive in one direction, connecting at least two deflecting devices of a traction device to the printing head through a connection, and offsetting the guide device, carried by the printing head, transverse to the given direction when a connection region of the printing head and the traction device passes one of the at least two deflecting devices.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a printing apparatus and a printing method with a movable printing-head guide, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.